During blow molding processes and, especially, extrusion blow molding processes, flash is often formed along a portion of a parting line of the molded plastic article. The bottom or base of the article may have a “tail” flash, for example, which is the result of clamping the plastic that is extruded between the two mold halves. In addition, unwanted plastic flash is often attached to the top of the article adjacent to where the threads of the article are formed. If the article has a handle, the section between the handle and the body of the article may also contain a web of plastic material corresponding in thickness to two layers of the original plastic parison.
There have been a number of different approaches taken to address the problem of removing flash from blow molded plastic articles. Conventional de-flash apparatus on the market operate in an indexing motion. A bottle is brought into the apparatus, the bottle is stopped, the bottle neck is held stationary between two dies while a cutting blade de-flashes the bottle, and then the bottle is removed from the apparatus. The apparatus then indexes and repeats the process for the next bottle. Starting and stopping the motion of a bottle causes efficiency issues with the production line and also reduces line throughput. Indexing machines typically cannot index more that 30-35 indexes per minute. This means that each index must de-flash many bottles at once in order to reach production line rates. Tooling is also expensive for this type of apparatus because it typically uses a long chain with bottle-specific nests to transport the bottles between stations.
Autotec Engineering of Sylvania, Ohio, provides a conventional indexing de-flash trimming apparatus. See www.autotecinc.com. Bottles arrive at the apparatus laying down. The bottles are loaded into a basket by a robot, and are transported to the apparatus via indexing. A punch closes on the bottle and removes (knocks off) the flash. The apparatus then indexes. The Autotec apparatus is limited to about 140 bottles per minute; thus, the index system is time limiting.
Other de-flash apparatus trim bottles as the bottles move continuously along a path, thereby increasing the production rate. As described in U.S. Pat. No. 6,360,414, Uniloy Milacron Inc. of Manchester, Mich., offers a continuous motion rotary de-flashing apparatus. The de-flashing apparatus is a dual rotary trimmer having two, balanced, continuously counter-rotating wheels, namely a nest tool wheel and an intermeshing trim tool wheel. Each wheel rotates along a circular path. When the two circular paths tangentially correspond, the two wheels mesh. A screw advances the articles sequentially into engagement with the trimmer whereby the articles are de-flashed of the tail, body, and top flash when the nest tool is in juxtaposed position with the trim tool. As a result, states the '414 patent, the article is nested, trimmed, and released in one continuous motion.
One issue with the continuous apparatus disclosed by the '414 patent is that the tooling only makes contact for a fraction of a second when the two wheels meet. This configuration limits the amount of flash material that can be removed. Further, some flash can be difficult to trim because the tooling meshes like gears. The apparatus is likely to experience problems with stretching, for example, rather than cleanly shearing more ductile plastic materials. Still further, the sliding movement of the trim tool adds radial shear force to the tangential shear force and risks less-than-clean shearing of flash from certain containers—especially those containers made of more ductile plastic materials.
U.S. Pat. No. 7,752,947 issued to Fiorani et al. discloses a bottle trimmer and method of cutting or trimming a plastic log ejected from a blow mold to form multiple open-mouthed bottles. The log has respective bottle portions on opposite ends of the log with each bottle portion having an offset neck. The bottle portions are connected in neck-to-neck relationship by a neck ring having a central neck axis. The trimmer and method are especially suitable for high-output production lines. A log conveyor is continuously moved along an arcuate path (reference number 320 in FIG. 27 of the '947 patent). Flash is removed by a punch engaging the log while the log is carried on a wheel rotating in a circular portion of the actuate path. The circular path of the de-flash operation disclosed by the '947 patent limits significantly the amount of time available for that operation. After de-flashing, the body to be trimmed is placed between holders carried by the conveyor and trimmed by rotating the holders about the offset neck axis as the conveyor moves past a stationary trim knife extending along the path.
Each of the known continuous apparatus are relatively expansive, complicated, costly, and heavy in weight. The de-flashing operations are completed using arcuate, often circular, paths which limit the time available for the operation. Such paths also detract from the directed, tangential force that maximizes the efficiency and effectiveness of the de-flashing cut or trim.
To overcome the shortcomings of conventional apparatus, a continuous motion de-flash trimming machine is provided. The machine picks up a bottle, removes the flash from the bottle, discards the unwanted flash, and releases the de-flashed bottle in one continuous motion. An object of the machine is to perform the de-flashing operation continuously, rapidly, and reliably to maximize throughput. A related object is to provide a machine capable of de-flashing bottles at a rate equal to the rate at which the blow molding equipment produces the bottles. A further related object is that the machine provide a relatively long, straight path for the de-flashing operation and avoid the arcuate, often circular, paths that limit conventional apparatus.
The de-flash trimming machine must be both compact and able to be oriented in-line with the blow molding equipment so as to minimize factory floor space. Another object of the machine is to provide the versatility needed to operate in connection with a wide variety of production lines and to accommodate various types, shapes, and sizes of bottles. A related object is to provide a machine that can accurately orient bottles before de-flashing to permit de-flashing without damage to the bottles. Yet another object is to provide an economical machine that saves money when installed in a plant or factory. It is still another object of the present invention to provide a machine that is sturdy, relatively light, easy to use, and reliable.